Fusible thermometer



May 4, 1954 R. w. sMrrH ET Al.

FUSIBLE THERMOMETER Filed March 21, 195o ,7 Trai/M675.

Patented Mey 4, 1954 FUSIBLE THERMOMETER Rossman W. Smith, Pleasant Ridge, and George E. Underwood, Jr., Royal Oak, Mich., assignors to Smith & Underwood, Royal Oak, Mich., a

partnership Application March 21, 1950, Serial N o. 150,888

4 Claims.

The present invention relates to fusible thermometers, and particularly relates to improvements in fusible thermometers of the type disclosed in United States patent to Diack, No. 1,000,673.

Fusible thermometers of the type to which the present invention directed comprise transparent tubular members having fusible pellets disposed therein. The fusible pellets are formed of a selected chemical, or combination of elements, having known fusing temperatures. The thermometers are employed to indicate that articles with which they are used have been subjected to certain predetermined temperatures for certain predetermined lengths of time. For example, they are employed to indicate the temperature and time attained in articles or chambers, such as chambers designed for use in sterilizing rolls of surgical dressing; for indicating that liquids, such as milk and infant formulas, have been properly sterilized; and for indicating that food products, such as meat, have been cooked for the proper length of time at proper temperatures. These uses are mentioned by way of example, and the thermometers of the present invention are capable of other uses as Well as those mentioned.

One of the prima-ry objects of the present invention is to provide an improved fusible thermometer that may be read more quickly and more accurately than such prior thermometers.

`A further object of the invention is to provide an improved fusible thermometer in which the initial melting of the fusible pellet will be quickly evidenced before the pellet is completely broken down.

A further object of the invention is to provide an improved fusible thermometer which is adapted for more fields of use than previous ones.

A further object of the invention is to provide improved fusible thermometers which may be used in any position.

A further object of the invention is to provide an improved fusible thermometer which may be inserted in the object being treated, either from the top or from the bottom.

Other objects of the invention will become apparent from the specification, the drawing relating thereto, and from the claims hereinafter set forth.

Referring to the drawing in which like numerr als are used to designate like parts in the several views throughout:

Figure l is a View of a fusible thermometer, with parts in cross section, illustrating one form of the present invention;

Fig. 2 is an enlarged cross-sectional view, taken substantially along the line 2--2 of Fig. 1;

Fig. `3 is a front View illustrating a modified form of a fusible thermometer;

Fig. 4 is a cross-sectional view taken substantially along the line 6 4 of Fig. 3;

Fig. 5 is an enlarged cross-sectional View taken substantially along the line 5-5 of Fig. 4;

Fig. 6 is a view similar to Fig. l and illustrating a modified form thereof;

Fig. 7 is an enlarged cross-sectional View taken substantially along the line 'F-l of Fig. 6; and

Fig. 8 is a broken view, similar to Fig.` l, and illustrating a modification thereof.

Referring to Figs. 1 and 2, one form of the present invention is illustrated which comprises an elongated transparent tubular member l, sealed at the bottom, as indicated at 2, and sealed at the top, as indicated at' 3. The top is preferably indented to form a neck, as indicated at 4, to which a thread 5 may be tied. The knob and the thread 5 may be used if the tube is to -be suspended in a liquid, and the knob indicates the top for proper positioning. However, the tube may merely be dropped into the liquid without the thread 5. The tube l may be formed of transparent glass or transparent plastic, as desired.

A fusible pellet 6 is disposed within the tube l and is supported from the bottom by means of a transparent capillary tube l. The pellet 6 is generally cylindrical in form and is formed of a selected chemical such as resorcinol; including a dye, and having known fusing temperature.

When the thermometer is placed in the object being treated, such as within the bottle of milk or infants formula, the bottle containing the milk is placed in the usual sterilizing equipment. After the heating process, the tube may be seen through the bottle, and when the milk has been subjected to the proper and required sterilizing temperatures for the proper required length of time, the pellet E will have completely melted. Since it is held away from the bottom of the tube by the capillary tube, during the initial melting, the material from the pellet 6 will run down into the tube 'l so that the tube is partly lled, and this initial melting can thus be quickly observed.

In the embodiment shown in Fig. l., only one capillary tube is shown on one side of the pellet 6, but it will be appreciated that another capillary tube may be disposed on the other side of the pellet so that the tube cannot be misused with respect to the way that it is dropped into the bottle. With tubes at both sides of the pellet, the thermometer may be dropped in in either direction.

Referring to Figs. 6 and 7, a modified form is illustrated in which, instead of using a capillary tube i to support the pellet E from the end of the tube, elongated members 8 and t are em'- ployed on opposite sides of the pellets 6 and such members 8 and 9 are formed of an absorbent material, and may be wooden toothpicks. The

thermometer is employed in the same way as that described above, and as soon as the pellet, which contains a dye, begins to melt, such dye from the pellet will be absorbed by the supporting members 8 and 9 and thus cause discoloration which can be quickly and easily observed. The pellet itself may be screened by an opaque portion 20, which may be in the form of a paint coating in the region of the pellet. Thus, the observation will be positive when the supporting member 8 is discolored. This screening of the pellet may also be employed with the other embodiments.

Referring to Figs. 3-5, another form of the invention is illustrated which is particularly designed for use in testing the proper cooking of meat. An elongated tubular member is indicated at I9, and may be formed of a transparent glass or transparent plastic material. It is closed at both ends; one end being formed with a sharp point I I, and the opposite end being formed with a gripping tab I2. In this embodiment, two pellets I3 and Il are disposed within the tube and supported away from one end by means of an indentation I5, which is formed in the wall of a tube, and which projects in the path of the pellets to hold them away from one end; in the embodiment illustrated, the bottom end. It will be appreciated that a similar indentation could be formed in the tube I on the opposite end of the pellet so that they would be supported in spaced relation to both ends.

The pellets i3 and I4 are selected with different melting points. For example, pellet I3 may melt at 150, while pellet I4 will not melt until a temperature of 160 is reached. Thus, the tube I0 may be inserted into meat from the bottom, and by observing the condition of the pellets, it can be determined whether the meat on the inside has been properly cooked. If the pellet I3 has begun to melt, the melted portions will drop to the bottom exposed portion I0, so this can be observed without removing` the thermometer. Melting of the pellet I3 indicates that the meat has reached the proper temperature, while breakdown or melting of pellet I4 will indicate that the meat has been overcooked.

By disposing the pellets I3 and I4 on the opposite side of the indentation I5, the thermometer may be inserted into the top of the meat; or, by providing indentations on both sides of the pellets, the thermometer may be placed in either the bottom o1' top of the meat. The form shown in Figs. 3 and e is preferred because, by inserting the thermometer in the bottom of the meat, the droppings from the melting pellet I3 can be quickly observed in the bottom of the tube without removing the thermometer.

In the embodiments described above, the lengths of the tubes may vary, depending upon the size of the containers holding the liquid to be tested, or the size of the object into which the thermometer is inserted. The melting points of the pellets will depend upon the nature of the objects being tested. For example, when employed to test infants formula, such pellets may be formed of resorcinol, which fuse or begin to melt at temperatures of 230 F. When employed with meat, for example, they may be formed of natural waxes, such as beeswax, which will melt at temperatures of 152 F. The compositions of the pellets may vary, as substances having the predetermined temperaturesand time factors involved are well known to chemists in this eld.

The time factor may be :varied in several ways. For example, the time factor may be varied by varying the size of the pellet; i. e., a large pellet will take longer for complete melting than a. smaller pellet of the same material.

Another manner in which the time factor may be varied is illustrated in Fig. 8. The tube, such as tube I as illustrated in Fig. 1, may be /inserted in another tube 2l, so that the periphery of the tube I is spaced from the inner surface of the outer tube 2|, which has an insulating effect. In this embodiment, only two tubes are shown as being used, but additional tubes may be employed to get the time factor desired. The outer tube 2| is sealed at both ends and is employed as a unit in the same manner as the embodiments described above.

Formal changes may be made in the specific embodiment of the invention described without departing from the spirit of the invention, the scope of which is commensurate with the appended claims.

What is claimed is:

l. A fusible thermometer comprising an elongated transparent tubular member, a fusible body therein having a predetermined melting point, and non-:fusible elongated and rigid members of absorbent material within said tubular member on opposite sides of said fusible body to hold said fusible body away from both ends of said tubular member.

2. A fusible thermometer comprising an elongated transparent hollow member closed at both ends, a fusible body therein having a predetermined melting point, and a non-fusible elongated rigid member disposed within said hollow member in one end thereof and terminating short of the opposite end thereof, said rigid member terminating under said fusible body and supporting said body thereon in spaced relation to said one end of said hollow member.

3. fr fusible thermometer comprising an elongated transparent tubular member closed at both ends, a fusible body therein having a predetermined melting point and a non-fusible elongated rigid transparent hollow tubular member disposed within said nrst tubular member in one end thereof and terminating short of the opposite end thereof, said hollow member terminating under said fusible body and supporting said body thereon in spaced relation to said one end of said tubular member.

4. A fusible thermometer comprising an elongated transparent tubular member, a fusible body therein having a predetermined melting point, and a non-fusible elongated and rigid member of absorbent material within said tubular mem-v ber in one end thereof and terminating short of the opposite end thereof, said rigid member terminating under said fusible body and supporting said fusible body thereon to hold said fusible body away from said one end.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,280,681 Atkinson Oct. 8, 1918 2,335,999 Diack Dec. 7, 1943 2,460,215 Chase Jan. 25, 1949 FOREIGN PATENTS Number Country Date 238,394 Germany Sept. 23, 1911 

